Air University Review, January-February 1981
precursors and problems
Kenneth P. Werrell
A cruise missile can be defined as a dispensable, pilotless, self-guided continuously powered, air-breathing warhead-delivery vehicle that flies just like an airplane, supported by aerodynamic surfaces.1
The years 1976 and 1977 marked a turning point in U.S. Air Force history. During those years the cruise missile was tested, a weapon with remarkable performance and the promise of relatively low cost. Clearly, the cruise missile was material in the cancellation of the B-1 bomber. For years the Air Force had been seeking a follow-on to its 1950 state-of-the-art B-52s, but efforts with the B-58 and then the B-70 had failed. Great hope was placed on the B-1, but questions as to its cost and ability to penetrate to the target led to President Carter’s decision in June 1977 to put it aside. In short, the B-1 was judged not to be as cost effective as the air-launched cruise missile (ALCM). What is this cruise missile that will change Air Force weapons and thinking? What is its background?
While the name may be new, it turns out that what we today call a cruise missile has been around for quite a while, though known by other names. From the outset, it was recognized that unmanned aircraft possessed a number of advantages over manned aircraft. The primary selling point was low cost. Because the weapon was a one-shot deal, expected to perform only once and then for a few hours at most, cheaper materials lower manufacturing tolerances, and other shortcuts could be made in design and production. The absence of a crew member and associated safety devices, instrumentation, and safety factors in engine and airframe further cut weight, complexity, and cost. A second major advantage was that a crewmember would not be subjected to hostile fire.
But throughout its history, the unmanned weapon had to overcome a number of inherent problems, and its present-day success is due to the triumph of incremental technology over these problems. Probably the most difficult of these has been guidance. The absence of a pilot meant that the device had to be guided by some other means. The early primitive guidance systems created problems of accuracy, especially serious considering the small payload that could be carried. The earliest cruise missiles were typically guided by nothing more than a gyroscope that kept the heading more or less constant, supplemented by a barometric device of some sort to roughly control altitude, plus a timer to determine range. The result was low accuracy.
Low accuracy meant that only large targets could be engaged effectively. Another problem has been vulnerability. Without active defenses and unable to maneuver if attacked, the unmanned aircraft had to depend on speed, numbers, and surprise to get through. These problems were characteristic of cruise missiles from the start and were only gradually overcome.
As early as 1914, the British began experiments with a pilotless aircraft under the direction of A. M. Low. The same idea was considered in other countries as well, including the United States and Germany. In fact, a number of pilotless aircraft actually flew before the end of World War I. A U.S. Navy project was associated with Glenn Curtiss, while an Army project is linked with a team led by C. F. Kettering and Elmer Sperry. The latter produced and tested the "Bug," made of papier-mâché and wood, weighing 300 pounds and capable of carrying a 300-pound warhead about 50 miles. The cost? —about $400.
But the end of the war brought a quick halt to this and many other promising ideas. Discussions concerning unmanned aircraft continued in the interwar years, but the rapid development of conventional aviation and the scarcity of money for the military, especially after the Stock Market Crash of 1929 and the ensuing depression, prevented much more than just talk. An exception was in Britain, where pilotless aircraft research and development was actively pursued. In 1929, for example, the Royal Air Force tested the Larynx (Long Range Gun with Lynx engine), but that was about the extent of it.
When the United States entered the war in December 1941, our airmen saw the four-engine bomber as their major weapon. Nevertheless, the Army’s top airman, General Henry H. "Hap" Arnold, noted that the "Bug’ had been upgraded. By 1941 latter-day descendants of Kettering’s pilotless bomber were capable of hauling a 800-pound warhead 200 miles. Other improvements included radio control guidance compared with the preset arrangement in the vintage 1918 "Bug." But the American airmen had invested too much into their concept of strategic bombing to give such a weapon really serious thought. Early American cruise missile developments in World War II thus lacked not just a commitment in equipment, training, and doctrine but, maybe even more important, an emotional commitment. In addition, and ultimately more compelling, the pilotless aircraft lacked the range, accuracy, and payload that the airmen calculated would be needed to do the job—and, even then, these calculations proved to be somewhat optimistic. World War II, from the American airmen’s point of view, was a war of precision strategic bombing and the inaccurate, low-yield cruise missile had no real place in their scheme of things.
Not that the airmen were immune to technical change, but iron bombs dropped by four-engine bombers flying in tight formation in daylight was the way it was done in the "Big War," especially against Germany. Operational experiments were conducted with remotely controlled, guided, free-fall bombs and with both guided and unguided glide bombs. In another effort, old bombers were stripped of equipment, to be crammed with explosives and sent toward German targets. Controlled by radio devices, the last versions were equipped with television for terminal homing accuracy. But despite considerable effort, technical problems thwarted the success of all these projects.
The German genius created, developed, and put into operation both air-breathing and ballistic missiles during World War II. It is with the air-breathing V-1 buzz bomb that the operational history of the cruise missile really begins, for the V-1 was the first pilotless bomber ever to be employed in large numbers and with effect. While the development of the spectacular V-2 ballistic missile need not detain us here, the simultaneous development and operation of the two does point out the problems and relative advantages of each.
The V-1 was made possible by mating a pulse-jet engine to a very simple airframe, a cheap and effective combination. In contrast, the V-2 cost between four and twenty or more times as much to build as did the V-1, depending on how the costs are calculated. Yet, in most ways their performance was remarkably similar. The accuracies of the two were comparable, 80 percent of the V-1s impacting within eight miles of their aiming point. Each carried a warhead of about 2000 pounds out to a range of about 150 miles. In the summer of 1944, the two were launched against Britain, causing considerable damage and widespread concern. Anglo-American countermeasures highlight one major difference between the two missiles: once the ballistic V-2 was launched, there was no stopping it, unlike the winged V-1 which could be intercepted.
One defensive measure was to attack the facilities and bases linked with the V-weapons. The American and British strategic bombers pounded these targets but could only delay, not stop, their employment. At the same time, the bombing of the V-weapon targets was a drain on the strategic bombing offensive as well as support of the Anglo-American land offensive.
A second method was indirect, a clever British deception that emphasizes the need for accurate and timely target information. Because of the lack of German aerial reconnaissance, the British control of both obituaries that appeared in the British press and espionage reports sent back to Germany through agents controlled by the British, the Germans were convinced that their missiles were impacting beyond their aiming point. In fact they were falling short, and with each German correction, they fell ever shorter.
Although the V-2s could not be intercepted in flight, the V-1s could be and were. The 400 mph buzz bomb was essentially defeated by conventional means. Interceptor aircraft, barrage balloons, and a thick screen of flak (including the first use of proximity fuzes in Europe) knocked down about half of the V-1s launched, 75 percent in the last week of the campaign.
The capture of the V-weapon launching sites by the advancing western armies ended the campaign. While some V-1s were later air-launched, the major assault of Britain was over. In all, about 8000 V-1s were launched against Britain, killing 6000 Britons. Another note of interest to current planners, the Anglo-American defenses cost about four times as much as the German’s missile offensive. In World War II, however, the Anglo-Americans could well afford the cost; the Germans could not.
The relative success of the V-1 reawakened American interest in cruise missiles; using captured components and doing little more than copy the German original, the U.S.A.A.F. built its own version of the V-1 in 60 days. The awakened interest in missiles did not die after the war. The capture of the Germans’ designs, equipment, factories, and personnel permitted the victorious powers to capitalize on the work the Germans had done in propulsion and guidance. More important, however, was the development of the atomic bomb. With such warheads, the accuracy problem was essentially resolved.
The Navy developed the Regulus missile, which first flew in 1951. It had a range of about 500 miles and flew at a speed of about 600-mph. The missile was operated from the decks of submarines (four converted subs and one nuclear one), aircraft carriers, and cruisers. The Regulus became operational in 1955 and the last was delivered to the Navy in 1959. An advanced version, the Regulus II, had a range of more than 1000 miles, but it was canceled in 1958.
The postwar Air Force program produced a number of winged missiles, the most successful of which was the Martin Matador. Originally designated the XB-61, its design phase began in 1946 with the first model flying in January1949. It had a range of about 600 miles and a speed of 650 mph. The Matador became operational in Germany in 1954, and the thousandth copy was delivered in 1957.
The Matador was succeeded by the follow-on TM-76 Mace, which first flew in 1956. Although its flight performance was slightly better than that of the Matador, the real difference between the two was the Mace’s better guidance. Compared to the ground control guidance system of the Matador, the Mace (TM-76A) was fitted with a map matching navigational system (ATRAN), while another version (TM-76B) was guided by an inertial navigational system. Eventually the Mace was to have a range of 1200 miles and a speed of about 650 mph.
At the same time, work was being done on strategic range winged missiles. The development of the tailless Northrop Snark began in i946 under the designation of B-62. Redesignated SM-62A, it had a range of over 5500 miles at a speed of about 615 mph. The 60,505-pound missile was tested over a 5000-mile range in 1957 and was to be guided by an inertial system with a star-tracking device. It got into the inventory in the early 1960s; however, after 30 of them were declared combat ready in only four months, the Snark unit was deactivated.
The Air Force's other winged strategic missile did not get even that far though it produced a wealth of data for later high-speed, air-breathing projects. The North American XSM-64 Navaho was to be powered by two ramjets after being launched vertically in piggyback fashion on a booster rocket. It also had a 5000-mile-plus range and was supersonic with the capability to fly at the speed of mach 2.5 and 75,000 feet. But that performance did not come without cost; the Navaho tipped the scales at over 120,000 pounds, and the size of Navaho’s budget raised congressional eyebrows. Thus the cheaper Snark and the prospect of ballistic missiles led to its demise in the mid-1950s.
By the late 1950s and early 1960s, most attention had shifted from unmanned winged missiles to ballistic missiles. Even a cursory check of military periodicals of the period shows that very little was written on winged missiles in the 1960s and 1970s. The primary work with the air-breathing devices was done as aids for the bomber force, both as standoff and decoy missiles. While the rocket-propelled Rascal was developed to be used with the B-47, two air-breathing missiles were developed for use with the B-52. The North American Hound Dog was a standoff weapon that came into service in the 1960s with a 700-mile range and speed exceeding mach 2. Two were carried externally by a B-52, each armed with a one-megaton warhead. The McDonnell-Douglas Quail was a decoy missile that simulated the appearance of a B-52 to hostile radars and had a range of over 200 miles. Until the latter part of the 1970s, it seemed that the winged missile was destined to be but a tool for manned bombers.
Then came what has come to be called the cruise missile. What made it a viable weapon was the perfection of map matching technology and the development of highly efficient miniature jet engines. Small, highly precise, inertial navigation units—a far cry from the "Bug’s" crude barometers and gyroscopes—provided a reliable basis for precise navigation; high-speed microcomputers and miniaturized radar circuitry allowed the missile to update its position for terminal accuracy by matching the contours of the ground below the missile with a radar map stored in the computer’s memory. Two different designs were considered by the United States, the General Dynamics AGM-109 and the Boeing AGM-86. The two had similar characteristics and performance, a range of over 1300 miles and a speed of just under 500 knots. The Boeing version was ultimately chosen for production.
The big advantage of the cruise missile is its smallness and cost. The missile's small size and weight of less than 3000 pounds enables an aircraft to carry a great number of them: a projected 18 by a B-52 (in comparison with only two Hound Dogs) or as many as 50 by a Boeing 747 or similar wide-bodied transport converted into a missile carrier. Its small size also improved the weapon’s chances of penetration, especially when combined with its ability to fly along the contour of the earth, as low as 20 meters above a level surface or within 100 meters of mountainous terrain, according to some published reports. The map matching system (TERCOM) is combined with an inertial navigational system in a system called TAINS. This not only gets the cruise to its target but also with an accuracy heretofore unheard of for an intercontinental weapon: less than 100 meters, an accuracy that brings the cruise missile full circle by making nonnuclear warheads feasible. It costs $1,000,000 a copy—a far cry from the $400 for the "Bug" or $13,000 for the V-1--but in today’s economy a million is cheap, thus allowing a great many of them to be purchased. It should be emphasized that there is much to be said for quantity, a factor we in the West have tended to underrate. In short, the cruise missile’s relatively low cost and high performance make it a very cost-effective weapon.
The recent revelation of "Stealth" technology makes the cruise missile potentially even more attractive, as it offers the possibility of greatly enhanced ability to penetrate hostile airspace. The prospect of large numbers of these small, accurate low-flying missiles must create nightmares for Soviet defense planners.
The unmanned winged missile has come a long way since 1914. Incremental technology has surmounted problems of range, guidance, warhead, accuracy, and vulnerability, producing a weapon which, while identifiably the same thing, promises to have quite a different net effect. Some believe that the United States has a ten-year lead on the Soviets with this new weapon, a military advantage of potentially enormous importance. But the march of advanced technology is relentless and cannot be underestimated. Certainly, the Soviets have in the past proved their determination and ability to catch up in a hurry. Lest we forget, similar and even longer delays were forecast concerning the Russians’ ability to develop the A-bomb. In fact, it took them four years.
1. Kosta Tsipis, "Cruise Missiles" Scientific American, February 1977, p. 20.
Kenneth P. Werrell (USAFA; Ph.D., Duke University) has taught recent U.S. and world military history at Radford University since 1970, except for one year as visiting lecturer in military history at Army Command and General Staff College. He has published numerous articles in historical and military journals and has just completed a book-length manuscript on the Eight Air Force in World War II. Currently, he is working on an annotated bibliography of that organization for the Eight Air Force Historical Society. He is a frequent contributor to the Review.
The conclusions and opinions expressed in this document are those of the author cultivated in the freedom of expression, academic environment of Air University. They do not reflect the official position of the U.S. Government, Department of Defense, the United States Air Force or the Air University.
Air & Space Power Home Page | Feedback? Email the Editor